1. Field of the Invention
The present invention relates generally to an apparatus for holding a heat exchanger core during a brazing operation.
2. Background Information
Typical heat exchanger cores are manufactured by assembling a plurality of tubes-interleaved with fins between a pair of side support members. The core is precompressed by a variety of known methods prior to the brazing operation to maintain the tube and fins in proper relationship. One known method is to precompress the core with a steel band surrounding the core before brazing. After banding, the core is inserted into a furnace and heated until it brazes together. Following the brazing process, the steel bands are cut off each heater core and discarded, resulting in a large amount of waste. In addition, these bands often distort and/or skew the core which can result in leaks and/or improper vehicle fit.
Other types of brazing fixtures have been proposed such as that shown in U.S. Pat. No. 5,165,163, assigned to the assignee of the present invention. In that system, the brazing fixture includes a pivotal lever which applies a compressive force against one of the side support members while the other side support member is held stationary in the fixture. However, these fixtures tend to become corroded in the brazing atmosphere, reducing the effectiveness of the compressive force applied against the core. Also, these fixtures usually are not used upstream of the braze process due to sheer weight and bulk.
A third type of brazing fixturing is proposed in U.S. Pat. No. 3,894,580 and which is shown schematically in FIG. 1. In FIG. 1, a heat exchanger core 10 includes a pair of side support members 12 disposed on opposite sides of an assembly of a plurality of interleaved tubes 14 and fins 16. A pair of header assemblies 18 are disposed on opposite sides of the heat exchanger core in known construction. In this prior art system, a pair of generally parallel ties 20 extend between each of the side support members 12 to fix the core in a predetermined position prior to the brazing operation. The disadvantages of using the generally parallel ties 20 is that unless an elaborate and complicated clamping mechanism, such as shown in U.S. Pat. No. 3,894,580 is utilized on each end of the ties 20, the heat exchanger core can still skew as a result of normal process handling and/or shrinkage and thermal cycling during the brazing operation. This skewing or misalignment of the heat exchanger core often results in deleterious effects upon the core such as leaking and/or improper vehicle fit.
It would, therefore, be advantageous to provide an effective, simple fixturing apparatus which can easily be used during the fabrication, processing, and brazing of the heat exchanger core to prevent the skewing or misalignment of the heat exchanger core.